Traditional meters have had difficulties measuring the volumetric flow rate of liquids exiting a three phase separator. An inlet allows a mixture of fluids to enter a three phase separator. The mixture of fluids consists of two liquids and a gas. The gas is emptied out of the three phase separator by a gas outlet. A dump valve siphons a liquid, such as water or oil, out of the three phase separator by extending the siphon into the liquid with an extension fitting. The liquid is carried away from the three phase separator along a dump liquid line. Tradition meters measure the volumetric flow rate of the liquid being carried along the dump liquid line.
Some traditional meters include differential pressure meters, positive displacement meters, velocity meters, and mass meters. Differential pressure meters, also known as head meters, are installed on the dump liquid lines outside of the three phase separator. Differential pressure meters experience problems with gas in the dump liquid lines because these meters are not completely submerged in the liquid being measured. Gas bubbles form in the sensing lines of these meters and create inaccurate readings. Differential pressure meters need to be continuously maintained by bleeding the gas bubbles from the sensing lines. Positive displacement meters have problems with installation, moving parts being damaged, accuracy, and reliability. Velocity meters undergo problems with installation, moving parts being damaged, accuracy, reliability, cost, conductivity of liquids, sensor coating, and noise interference. Mass meters experience problems with installation, cost, reliability, errors caused by gas pockets in the exiting liquids, noise interference, and intermittent slug errors.
Problems with the traditional meters are solved by an internal liquid measurement and monitoring system. A pressure differential device such as a venturi tube is attached to the extension fitting, which submerges the pressure differential device in the liquid being measured. The sensing lines conveys the differential pressure to the sensor, which sends the measurement to an RTU flow computer. The RTU flow computer uses the pressure differential reading to calculate the volumetric flow rate of the liquid exiting the three phase separator. The RTU flow computer sends the volumetric flow rate calculation to a SCADA system, which records the calculation. The volumetric flow rate calculations are made in real time, and the SCADA system archives the calculations being made. This system has proven to be an accurate and reliable method to measure the volumetric flow rate through a dump valve, which allows operators to easily monitor and troubleshoot problems such as a leaking dump valve or a dump valve being stuck open.